Integrated circuit devices (i.e., integrated circuits) are formed on semiconductor substrates, or wafers. The wafers are then sawed into microelectronic dies (or “dice”), or semiconductor chips, with each die carrying a respective integrated circuit. Each semiconductor chip is mounted to a package, or carrier, substrate using either wirebonding or “flip-chip” connections. The packaged chip is then typically mounted to a circuit board, or motherboard, before being installed in an electronic or computing system.
Depending on the intended use of the semiconductor chip, one of the types of individual devices formed on the semiconductor substrate may be a micro-electromechanical system (MEMS) device. MEMS devices are often used in such devices as gyroscopes, accelerometers, resonators, filters, oscillators, switches, and variable capacitors. One particular type of MEMS device is known as an “interleaved” MEMS device. Interleaved MEMS devices are formed using many of the same processing steps, such as complimentary metal oxide semiconductor (CMOS) processing, that are used to form other devices (e.g., transistors) on the substrate and often incorporate a processing layer (e.g., polycrystalline silicon) that is also used to form a portion (e.g., a gate electrode) of one of the other types of devices.
After the various devices have been formed on the substrate, multiple insulating layers and conductors are formed on the substrate and over the devices to protect the devices, as well as provide contact pads so that electrical connections can be made to the devices, during what is referred to as “backend” processing. Additionally, particular types of MEMS devices, such as resonators, switches, and variable capacitors often require a cavity, often formed during backend processing, in which to move in order to work properly. The cavities formed around such MEMS devices are typically sealed to protect the MEMS device from contaminates and moisture, as well as provide a controlled-pressure atmosphere for specific types of MEMS devices. In order to form such a cavity, additional processing steps are typically required. These additional processing steps have been unsuccessful when using completely unmodified backend process integration. On the other hand such MEMS devices can be added to CMOS devices and sealed using processes and machines other than those used to form CMOS devices. As a result, the cost of manufacturing such devices is drastically increased.
Accordingly, it is desirable to provide a method for forming the cavities around the MEMS devices using the same processing steps used to form the devices and the backend layers on the substrate. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.